who has or can describe an Elwood 8x10 diffuser?

Hi:

I am wondering who among the 8x10 Elwood enlarger users here still has the glass diffusion plate in the lamp head, and can confirm my feeling it's placement would be closest to the negative stage. I also suspect the ones that used sheets of ordinary glass for heat absorption placed it above the diffuser.

If you REALLY want to be helpful, a photo or your best description of the approximate diameter of the most heavily blasted/ground region of the diffuser would give me an idea what it looked like (how Elwood accomplished a solution). I've read the Elwood 1929 patent, but think they made a variety of reflectors over the years (parabolic, elliptical and one other, I forgot). They may have made changes over the years too...

I just picked one up. I may try a sheet of opal glass above the negative stage, but am not opposed to trying my own grinding. I have equipment that would allow me to objectively measure luminance on the projection surface, and a densitometer. I know Jim Jones here just stacked sheets of hand ground glass until he was satisfied with the uniformity of illumination he could achieve.

I got mine without the glass. I had opal glass cut to fit and it has worked well. I have never had heat glass in it but I found a second dome and I am converting it to accept a hose to a ventelation fan to suck out the heat.

While Opal glass will work, it will dramatically reduce the light output. The gradiated sandblasted glass, thick in the middle, tapering off towards the outside is optimum. Heat absorbing glass always closest to the light source, to keep heat away from negative.

Mine didn't come with any of the glass pieces. To add to the confusion the drawings in my Elwood parts list show the sand blasted glass located on top of the 3 heat absorbing glass pieces. Glass is shown as 12x12 in. This is for the commercial C-2 model not early wooden ones. As far as bulbs go they recommend 300(150w) or 301(300w) but say that a 302(400w) can be used.

Speaking of construction differences...ChuckP, can you tell which 8x10 model or vintage mine is from a description?

Has 2-piece cast iron hinged vertical part with a 3-hole mounting pattern. The lower half of the lamp head I would guess is a different cast metal because it is not terribly heavy. At the rear of the lamp head is what looks like mahogany. The reflector looks to be parabolic and a hammertone green or khaki (? it's very dirty, hard to be sure). One handwheel for head height and a smaller handwheel for bellows adjustment. Has a 500W opal 302, which could be much newer than the enlarger, so that's not a useful clue.

Rauc-Im: I had a thought about directing heat to a negative dryer, but realized that would only be useful for drying negs at exactly the time the enlarger is running...pretty random chance of that...

Murray,
I had an Elwood similar to what you describe. The diffuser was a stack of 12 sheets of window glass. Very light frosting on the bottom one. The reflector is parabolic and about 22" high without going in the basement and measuring. The head was counterbalanced by a cast iron weight which rested on the back of the column. I could also tilt the enlarger for horizontal projection. I just kept the reflector. The previous owner used it for BW and colour. I did not like it that much as I found prints to be too soft compared to other equipment I had.

Looks like they did it many ways over the years, I guess changing when an improvement or deficiency was observed.

I wonder if results vary with one's lens of choice. I think this tells me the way to get uniform illumination is the method that works for me. Should I make a signature tagline 'the best diffuser is the one that works for you'? (Nah, maybe not).